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Recently, more power in a smaller volume is demanded from electric motors for next-generation applications. For this reason, permanent magnets are preferred in motor design. Although the use of magnets provides some advantages, it also has disadvantages such as designing difficulty and not starting directly from the line. However, by placing permanent magnets in the rotor of induction motors, which are widely used in the industry, line start Permanent Magnet Synchronous Motors (PMSMs) that can start from the line and continue to operate at a constant speed can be designed, in addition to their robustness and simplicity. With these motors which allow more power and higher efficiency to be obtained from the unit volume, the load and speed requirements of applications such as fans, pumps, and conveyor systems, which are widely used in the industry, can be provided without costly drivers. In addition, with the axial flux and radial flux topologies obtained by changing the flux direction for these motors, superior operating performance can be achieved, and material consumption can be minimized. In this study, the performances of two line start PMSMs with axial flux and radial flux, which have been prototyped and tested with a 4-pole 5.5 kW shaft power that can be driven directly from the line, are experimentally compared. The motor design parameters of both motors are also included in the comparison and the results are presented in detail. Both motors compared are prototyped motors for the first time, especially the axial flux structure is a structure that has been experimentally tested for the first time in the literature with the line start feature of the axial flux structure PMSM. The radial flux PMSM, on the other hand, has a hybrid slot structure, which has been applied for the first time in this field. The experimental comparison of these original structures for the first time in the literature constitutes the originality of this study. [ABSTRACT FROM AUTHOR]

Axial flux induction motors (AFIM) are gaining popularity due to their higher torque density than radial flux motors. However, axial flux motors have a more complex structure than radial flux motors due to their diameters expanding from the inside out. Before manufacturing, designers have two contradictory goals in the simulation phase. These are high accuracy and short analyses time. The finite element method is a commonly utilized technique for verifying designs. However, in the early stages of AFIM design, a 2D radial flux modeling approach can yield faster results. This approach is well-suited for radial motors, where 2D analysis is widely employed to achieve accurate designs within reasonable analysis times. However, for AFIM with a non-axisymmetric flux path, the application of 2D analysis poses some difficulties. This study compares three modeling approaches, linear, inner rotor and outer rotor modeling approaches to a 3D model and examines their steady-state performance. The results show compatibility in performance data, with some deviations in the torque-speed curve for inner rotor modeling and outer rotor modeling approach methods, which can be reduced by resizing the slots. Overall, acceptable errors and consistent results were achieved between the models. [ABSTRACT FROM AUTHOR]

In the present work, some tests on the electromagnetic interference issues of a new designed and constructed axial flux permanent magnet generator have been presented. The machine itself has multiple special laminated cores (i.e., 12) and 24 windings in the stator component with two active sides. Machine operates in 3 phases and uses disc type permanent magnets on two rotors at two sides in a sandwiched formation. Rotors have 32 magnets and freely rotates at the vicinity of stable stator within a certain air gap. The electromagnetic interference measurements have been realized for different distances and directions from the machine. Besides, the effects of different frequencies are also evaluated following the tests. It has been concluded that the shielding material shape is very important for the optimum shielding results. [ABSTRACT FROM AUTHOR]

Axial-flux permanent magnet (AFPM) machines are gaining popularity in low-speed and high torque applications due to their high torque density, high efficiency, and compact structure. In this article, a dual-rotor slotless AFPM (DRSAFPM) machine equipped with equidirectional toroidal winding (EDTW) is proposed and compared with that equipped with conventional single-layer and double-layer concentrated windings (CWs). First, the differences between the DRSAFPM machine with EDTW and that with conventional CWs in coil layout, electromotive force (EMF), and winding magnetomotive force are revealed. Considering the special coil layout of the EDTW, the coil factor and size equations of the DRSAFPM machines with EDTW and conventional CWs are presented. Second, the electromagnetic performance including air-gap field, back-EMF, torque, and efficiency of the DRSAFPM machines with EDTW and conventional CWs are analyzed based on the three-dimensional finite-element method. The simulation results validate the correctness of the coil factor and size equations and indicate the EDTW–DRSAFPM machine has superiority in back-EMF amplitude and torque density. Finally, a prototype of the EDTW–DRSAFPM machine is manufactured and tested, which validates the feasibility of the EDTW–DRSAFPM machine and the correctness of the analysis. [ABSTRACT FROM AUTHOR]

The aim of this study is to compare the axial flux induction motors (AFIM) used in electric vehicles by analyzing them with finite element method in different poles, number of slots and topologies. According to comparison, the most suitable one is determined as the drive motor for the reference electric vehicle. Output power of propulsion motor of an electric vehicle has been determined by considering different driving conditions. The dimensions and slot sizes of the induction motor that can provide the obtained output power have been calculated analytically. Double Rotor Axial Flux Induction Motors (DR-AFIM) calculations are presented as an example. Double Stator Axial Flux Induction Motors (DS-AFIM) and DR-AFIM topologies of 6-8-10 pole motors were analyzed using 3D models with combinations of 36, 48, 60 stator slot numbers and 52 rotor slot numbers in each motor. Copper is used in the rotor cage. In the stator windings, double-layer full pitch windings are used in each motor. Output powers, stator currents, efficiencies, power factors and current densities of the analyzed motors were compared at the same slip values. According to these comparisons, 8-pole DR-AFIM motors stand out in terms of the reference electric vehicle's ability to provide output power. The core saturations of the selected motor are shown on the quarter model, half axial 3D model of the motor. According to results, it is seen that the motor can be operated efficiently at an output power of nominal 50 kW, peak 75 kW and a rotor speed of 4000 rpm. In this study, AFIM in electric vehicles with double air-gap topologies were compared with different pole numbers and stator slot numbers. Accordingly, the most suitable one was chosen among them. The study will contribute to the researchers in terms of comparison of AFIM both in terms of double gap topologies and different pole and slot numbers. [ABSTRACT FROM AUTHOR]

This paper presents a new topology of an axial flux-switching memory machine with series-type permanent magnets (SPMs) to improve the flux regulation capability. The key idea was to combine low coercive force (LCF) PMs, which can be magnetized and demagnetized readily, with high coercive force (HCF) PMs in series to provide a variable air-gap magnetic flux. The flux regulating principle and the forward magnetization effect of HCF PMs on LCF PMs are presented and discussed. Based on 3D finite element analysis (FEA), the magnetization variation of LCF PMs and the electromagnetic performances of the machine under different magnetization states were investigated. Simulation results showed that the air-gap magnetic flux could be weakened by up to 45% by using a magnetization current impulse, significantly extending the PM motor's flux-weakening speed range. Finally, a prototype machine was built, and experiments were performed to validate the predictions. The basic experimental validation shows that the measured back-EMF and the flux regulating characteristic matched the 3D FEA results well. [ABSTRACT FROM AUTHOR]

Abstract—An artificial neural network (ANN) model is recommended for the analysis and prediction of the output results of a recently designed and constructed generator known as a permanent magnet generator with axial flux. The generator is considered to generate a power scale of P = 3 kW, especially for off-grid household usage far from the network. This machine has an adjustable air gap mechanism, and P = 3 kW is the maximum power; thus, this power can be decreased comfortably by increasing the air gap further to 7 mm. In this case, the maximum power rate can be decreased to P = 1.5 kW according to the experimental confirmation. As a new technique, an ANN approach is introduced for the predictions of voltage and power obtained output for various electrical loads, rotor speeds, and air gaps because it is difficult to get output values for all those machine parameters. In addition, this ANN technique enables one to find the generated voltage and power for specific extremely low air gap values (i.e., 0.2 mm, 0.4 mm, 0.6 mm), which is hard in experimental work due to construction difficulties. The ANN model is used to predict the output values of the generator before any laboratory practice successfully, and the users can determine the correct air gap ranges to their required power regimes for this generator. [ABSTRACT FROM AUTHOR]

The article deals with numerical analysis of a double sided coreless axial flux permanent magnet machine with two rotor disks and a coreless stator. Coreless stator represents copper windings which are held together by epoxy raisin, therefore a special focus has to be given to the stator temperature. In this article a numerical analysis is presented, which is based on the copper losses, namely the I2R product, where the resistance of the copper windings was both calculated as well as measured in the prototype machine. [ABSTRACT FROM AUTHOR]

The paper describes the effect of cooling media and temperature on 20 KW axial flux BLDC motor performance using numerical and experimental analysis. The motor is applied in electric car with initially as natural air cooling, and it is modified as liquid cooling. Numerical and experimental analysis shows that cooling temperature has significant effect on power and efficiency of motor. Lower cooling temperatures produce higher motor power and efficiency. Based on experimental investigation, maximum power of water cooled BLDC motor can generate power of 25 kW and 81.0 % efficiency, while air cooled motor produces lower power and efficiency of 19.1 kW and 65.0 % respectively. Comparative analysis of motor performance based on model and experiment were presented as well. Maximum motor power calculated by model is slightly higher than that measured by experiment. It can be explained that in modeling, the friction losses on the bearings are neglected, while in the experiment, the friction loss remains a variable that affects the motor power output. [ABSTRACT FROM AUTHOR]

Axial flux and radial flux cycloidal permanent magnetic gears are characterized by high gear ratios and high torque densities; however, their rotors experience large unbalanced forces, which stress the bearings used in the gear. This paper presents a new cycloidal magnetic gear topology that combines the radial and axial flux topologies. The paper analyzes the forces and torques contributed by the axial and radial magnets in this topology using 3D finite element analysis. It was found that the perpendicular force is necessary to transfer torque to the high-speed shaft and, thus, cannot be cancelled out, but the eccentric component of the magnetic forces can be largely cancelled out, potentially reducing bearing losses and increasing the lifespan of the bearings used in the gear. A proof-of-concept prototype was constructed. Experimental slip torque results matched 3D finite element analysis (FEA) simulations to within 15%, and testing showed that no-load losses were reduced and the slip torque was increased by combining both axial and radial topologies, compared to using an axial configuration alone. [ABSTRACT FROM AUTHOR]

In this article, an axial-flux permanent-magnet (PM) Vernier machine with the triple-stator, spoke-type PM rotor, and toroidal winding wound on the innerstator is proposed. Benefited from the flux focusing spoke-type PM rotor and short end length toroidal winding, the proposed machine has a high torque density and the improved power factor. Based on the air-gap permeance function, the analytical expression of the proposed machine is derived to qualitatively analyze the machine's performance. The quasi-three-dimensional (3-D) finite element analysis (FEA) is adopted to optimize the design parameters, such as innerstator diameter, PM thickness, and slot opening width. The quasi-3-D FEA results match well with the 3-D FEA. The 3-D FEA results show the torque densities of the proposed machine reach 49.4 Nm/L and 11.4 Nm/kg, respectively, under the 232 A/cm average electrical loading. The performances, such as overload capacity, PM demagnetization, and PM and core losses, are also analyzed by 3-D FEA. The comparison with the other axial-flux PM Vernier machine is conducted, and the results reveal that the proposed machine has the great advantages of the torque density and power factor. Since the prototype is not built, in this article, the assembly scheme and thermal behavior of the proposed machine are discussed. [ABSTRACT FROM AUTHOR]

In this study, the fully pitched axial flux switched reluctance machine (FP-AFSRM), which is a new configuration in the literature, was designed and 3D magnetostatic analyses were performed. The focus of the study is to produce higher torque density by simply changing the winding structure. Conventional SRMs are also known as short pitched SRM (SPSRM) since they have a short pitched winding structure. Fully pitched SRMs (FPSRMs) produce higher torque compared to SPSRMs with the mutual coupling effect between phases due to their fully pitched winding structure. In parallel with that, especially for electric vehicles, axial designs have increased gradually instead of radial design of electrical machines. For this purpose, the FP-AFSRM structure was proposed by combining axial design and fully pitched winding structure. The proposed FP-AFSRM model achieved up to 15.07% higher torque density than the basic SP-AFSRM model at different currents and equal copper losses. The proposed FP-AFSRM can be considered as an important alternative machine, especially for electric vehicle technologies and different technological fields, with the advantages of the high torque density and axial geometric structure. [ABSTRACT FROM AUTHOR]

This study is concerned with irreversible demagnetization faults in axial flux permanent magnet synchronous motors (AF-PMSM). Line start capability was provided to the AF-PMSM by making changes in its traditional rotor architecture. With this architecture, the motor operates as an asynchronous motor in the transient state and as a synchronous motor in the steady state. In this study, the impacts of an irreversible demagnetization fault on motor performance, which occurs in motors due to various reasons, is investigated. The four poles of the used AF-PMSM have 5.5 kW of shaft power. Each pole is comprised of five identical magnets. Different rates (20%, 40%, and 60%) of demagnetization failure were created in a single pole. The data acquired from the faulty motors were compared to data from a healthy motor. The results indicate that irreversible demagnetization faults have an adverse impact on motor performance. It was observed that the experimentally created demagnetization faults increase the current drawn by the motor. In addition, they cause a decrease in both the power factor and efficiency. However, the faults did not have an adverse impact on the starting capability of the motor. The unique aspect of the present study is that it is the first time the impacts of demagnetization faults on the performance of line start AF-PMSMs have been examined. [ABSTRACT FROM AUTHOR]

A comparative study of new partitioned stator hybrid excitation axial flux switching permanent magnet (HEAFSPM) motors with different partitioned excitation stator topologies for in-wheel traction applications is presented in this paper. The realization approaches of the partitioned stator HEAFSPM motor are discussed, and the motor topology with windings and permanent magnets (PMs) separately setting on different stators is selected in view of the advantageous structure for thermal management. On this basis, two partitioned excitation stator topologies including C-type tooth core and T-type tooth core stator configuration are proposed, and the air-gap flux modulation and flux regulation principle of the motors are analyzed. In addition, the design method of the partitioned stator HEAFSPM motor considering the effect of hybrid excitation sources is provided, and the two motors with different tooth cores are designed respectively. Meanwhile, for a fair comparison, the multiple objectives optimization method coupled with the sensitivity analysis is employed to optimize the two motors. The electromagnetic performances, anti-demagnetization capability, and flux regulation performance of the two motors are all investigated in detail. Finally, two prototype motors are fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the motor. [ABSTRACT FROM AUTHOR]

The paper presents 3D-FEA results of electromagnetic torque characteristics of a Field Control Axial Flux Permanent Magnet Machine (FCAFPMM) obtained for different pole shapes. The influence of the angular span of iron and permanent magnet poles on the cogging torque performance has been analysed at different excitations of an additional stator winding. [ABSTRACT FROM AUTHOR]

This article presents a generalization of an analytical model of an axial-flux permanent-magnet machine to any magnet shape. It uses an existing model, which computes the 3-D magnetic-flux density by the separation of variables and a finite-difference method. The original magnet shape is modified by adding a radial dependency to the Fourier series description of permanent magnets (PM) magnetization. The model is then developed for a general complex magnet shape. As an example, the model will be computed for a circular magnet shape and will be compared with finite-element analysis. [ABSTRACT FROM AUTHOR]

With the increasing requirements for miniaturization and high braking torque, it is now necessary to analyze the thermal characteristics to the same extent as the electromagnetic design for eddy current brakes. However, due to the lack of suitable convection heat transfer correlations for axial flux eddy current brakes, it brings difficulties to designers. To solve this problem, the correlations for an axial flux permanent magnet (PM) eddy current brake are derived using the computational fluid dynamics (CFD) and the least square method. The proposed correlations considered the changes in design parameters and temperatures of the eddy current brake, and the accuracy is verified by the CFD. Subsequently, convective heat transfer coefficients calculated through the correlations are assigned to a thermal network model of the eddy current brake, and the thermal network model is verified by experimental tests. The results show that the thermal network model can accurately predict temperatures of the eddy current brake. Since the time required to calculate convective heat transfer coefficients through the correlations is significantly less than that required through CFD, and the variation of the geometrical parameters and temperatures can be considered, these correlations are very suitable for use in the optimization process. [ABSTRACT FROM AUTHOR]

This paper presents an axial flux eddy current sensor with a compact and simple structure for measuring the rotating speed of iron shafts. The sensor structure is optimized for high sensitivity with a novel configuration of the coils positioned perpendicularly to each other. The sensor comprises two D-shaped excitation coils and two D-shaped pick-up coils in a double-layer structure. A disc-shaped magnetic shield or core shields the coils. Two iron shafts with different material properties are considered. A new cup-shaped configuration of nonmagnetic copper and aluminum caps mounted on iron shafts improves sensitivity and suppresses susceptibility to shaft material properties and airgap variation. 2D and 3D finite element methods are utilized for the performance analysis of the sensor. The measurements are performed at speeds up to ± 3000 rpm and different excitation frequencies from 400 Hz to 4 kHz. The eddy current speed sensor has excellent linearity characteristics with a nonlinearity error of 0.15%. The geometry of the coils is further optimized and improved for maximum sensitivity and compactness. The fault-tolerant capability of the sensor is also evaluated. [Display omitted] • Axial flux eddy current speed sensor for rotating speed measurement. • Novel configuration of perpendicular coils. • Optimization of the eddy current speed sensor. • 2D and 3D finite element method analysis. [ABSTRACT FROM AUTHOR]

In the present study, an artificial neural network (ANN) design has been proposed to analyze and estimate the output quantities of a newly manufactured generator, namely axial flux permanent magnet generator (AFPMG). The machine has been designed with a maximum power of 3 kW for the household electric power generation. As one of the innovative points, this machine has a variable air gap between the stator and the rotors, thereby the maximal power scale can be determined easily by adjusting the air gap between 2 mm and 7 mm. It means that the maximal power has values between 3 kW and 1.5 kW. ANN approach for such a machine is important in the sense that the estimation of output power, voltage and current values under various speeds and electrical loads are vital for the optimum operation of the machine. The designed ANN algorithm has been successful to estimate the output power and voltage of the newly produced generator for different air gap and speed and electrical load parameters. [ABSTRACT FROM AUTHOR]

Summary: An air gap optimization study of a 3‐kW axial flux three‐phase permanent magnet generator has been performed. The machine has two rotors sandwiching a stator with 12 separated laminated cores under an innovative flux morphology circulating over the back‐iron components. The rotor component has 16 rare earth magnets with an innovative self‐cooling blade structure. According to the air gap parametric magnetostatic analyses under the finite element method (FEM) between the range of 0.8 and 7 mm, the spatial magnetic flux distribution and cogging torque values have been determined. Besides, following the magnetostatic analyses, time‐dependent FEM simulations over the generated voltage and power values have been studied in detail. Then, after the implementation of the designed machine, the experiments have been performed for various air gap values. The generated power is observed to be dependent on the air gap, the efficiency is measured as 85%, and power density is measured as 111.7 kW/m3, which is a promising value compared to the literature. A scaling effect study is performed as functions of air gap and rotor speed for the first time to our knowledge. The maximum cogging torque is measured as 3.12 Nm. The other superiority of the present prototype is its low total harmonic distortion value within 2%; thereby, it generates nearly an ideal sinusoidal waveform. Consequently, the novel machine is recommended for both off‐grid and on‐grid operations with its low harmonic distortion and high efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a novel high-temperature superconducting stator-excited axial-flux magnetic gear (HTS-SEAFMG) for the high-torque transmitting system. The proposed magnetic gear combines the merits of both HTS-excitation and stator-excitation. By using the HTS-excitation, a high air-gap flux density can be easily obtained, thus achieving the high torque density. The HTS-excitation windings are placed on the stator with a static seal of cooling Dewar which greatly reduces the manufacturing difficulty and the cost of refrigeration system compared with the dynamic seal. Thanks to the stator-excitation pattern, both the high-speed rotor and the low-speed rotor comprise only iron, thus contributing to the high mechanical reliability. The axially sandwich structure can also simplify its assembly in the high torque transmission applications. The dimensional parameter optimization and the electromagnetic performance evaluation are conducted by using the finite element method, respectively. The results show that the torque density of the proposed HTS-SEAFMG can reach 123 kNm/m3. Theoretical analysis and results are both given to verify the feasibility of the proposed HTS magnetic gear design. [ABSTRACT FROM AUTHOR]

In high power density applications, such as electric or hybrid electric vehicles, heat extraction is a crucial aspect of electrical machine design due to stringent volume specifications. In these cases, it is extremely difficult, if at all possible, to satisfy the maximum temperature requirement when using conventional cooling systems, such as housing fins, shaft-mounted fans or even water jackets. To this end, a novel direct oil cooling system conceived for Torus-type axial-flux permanent-magnet machines is proposed here. In order to demonstrate its effectiveness, lumped thermal equivalent circuit simulations, finite element analyses and experimental tests are presented. The expected performances of the machine using the proposed direct oil cooling are compared to those obtained using state of the art water cooling. [ABSTRACT FROM AUTHOR]

This article presents a ring motor that is wrapped around the outer diameter of a propeller for electric rotorcraft. The approach is motivated by the greater aerodynamic efficiency afforded by larger diameter propellers with lower rotational speeds, ultimately minimizing battery energy requirements in electric rotorcraft. Lower rotational blade speeds are mismatched with electric machines that derive power density from high-speed operation, thus a machine design with very high torque density is proposed to allow lower speed operation without the aid of gearing. By wrapping the machine around the outer diameter of the blades, the innate lever arm drastically increases the torque density of the machine without the need for liquid cooling. An analytical design approach is used to characterize the machine design space and design outcomes are verified with finite-element analysis. The final prototype design targets the “heavy-lift” drone space and was tested to verify performance. Measurements of back electromotive force and max torque per amp, along with unloaded and loaded (propeller) testing, benchmark the design and highlight the relative impacts among the various loss mechanisms. The measured specific torque density of the air-cooled design is 6.25 N·m/kg – total mass, 11.1 N·m/kg – active mass only. Key areas for improvement, such as bearing drag reduction and winding fault tolerance, are identified. [ABSTRACT FROM AUTHOR]

This article proposes a novel axially magnetized Vernier permanent-magnet (AMVPM) machine which has permanent magnets (PMs) clamped on both ends of the rotor with alternately magnetized directions. The topology improves the mechanical strength of the structure without weakening the electromagnetic performances. The detailed operating principles are described and the design parameters are optimized. The open-circuit back electromotive force (EMF) is calculated analytically by using the harmonic series expressions. Then, a comparison between the AMVPM machine and regular Vernier permanent-magnet (VPM) machine is analyzed by finite-element analysis (FEA) method. Finally, the machine prototype is manufactured and the electromagnetic performances are experimentally validated. [ABSTRACT FROM AUTHOR]

India has enormous wind potential and average wind velocity is about 6 m/s, whereas the conventional wind turbine mechanism is operated at 7 m/s–12.5 m/s. It is necessary to design low speed wind energy conversion to harvest the electrical energy from wind. Mostly, Radial flux permanent magnet generator (RFPMG) is used for low speed wind turbine applications. This Conventional RFPMG has the drawbacks of low flux density and increase in weight due to large number of poles accommodation. In order to overcome the above setbacks, this paper proposes a double sided coreless axial flux permanent magnet generator (AFPMG) for low speed wind energy conversion applications. The performance analysis of the proposed AFPMG is carried out through finite element method using ANSYS Maxwell software. Finally the performance of RFPMG and AFPMG is compared based on the flux linkage, flux density, induced emf, stator current, moving torque, cogging torque, Total Harmonic Distortion (THD), material consumption, losses and efficiency. It is evident from the results that AFPMG gives the better performance than RFPMG in all such aspects. [ABSTRACT FROM AUTHOR]

The load angle of a synchronous generator connected to a power grid has an eigenfrequency that depends on the operating conditions. The existence of an eigenfrequency can make the generator sensitive to electrical and mechanical disturbances and motivates the use of damper windings and power stabilizing systems. Another reason for keeping load angle oscillations small is that they increase the eddy current losses in the stator core and clamping structure due to axial leakage flux. This is shown with transient finite element analyses and can be explained by a loss model derived from a phasor model of the eddy current loss density. [ABSTRACT FROM AUTHOR]

In industrial drive systems, one of the widest group of machines are induction motors. During normal operation, these machines are exposed to various types of damages, resulting in high economic losses. Electrical circuits damages are more than half of all damages appearing in induction motors. In connection with the above, the task of early detection of machine defects becomes a priority in modern drive systems. The article presents the possibility of using deep neural networks to detect stator and rotor damages. The opportunity of detecting shorted turns and the broken rotor bars with the use of an axial flux signal is presented. [ABSTRACT FROM AUTHOR]

The article deals with designing rotor disks of a double-sided axial flux permanent magnet machine, based on their deflection, due to the pull forces between opposite rotor disks, caused by the permanent magnets. Permanent magnets cause the magnetic flux density to flow between the permanent magnets on opposite rotor disks and its size determines the size of the pull force. That is why it is essential to determine the size of the axial component of magnetic flux density in the middle of the clearance between opposite rotor disks (fictitious air gap) in order to calculate the deflection of the rotor disks. The article presents a new method for determining the size of the axial component of magnetic flux density, based on a simplified finite element method and an approximation method as well as modified equations for determining the deflection of rotor disks. The method is used to determine the pull forces between rotor disks and based on the deflection of the disks an optimum rotor disk thickness can be selected in order to reduce the weight of the machine. [ABSTRACT FROM AUTHOR]

This paper deals with the development of a simplified numerical model with the aim of assessing the impact of using grain-oriented electrical steel (GOES) in switched reluctance machine (SRM) on its performance. Different grades of steel are studied to firstly analyze their impact on the inductance and the electromagnetic torque change. Then, both the simplified model and the steel grades helped determine the level of contribution of anisotropy and high permeability individually. In this paper, the impact on electromagnetic torque is evaluated along with a local analyses of the flux lines distribution and the numerical model allows to draw conclusions on the device performance when anisotropy is introduced. Although the GOES numerical model used for finite elements simulations is not a fully developed model, it is accurate enough for our study. The originality of this paper lies in the fact that the developed model is relatively simple and accurate enough to investigate all the electromagnetic phenomena and draw conclusions which can be applicable to a more complex and time-consuming electromagnetic device. The second original aspect is the introduction of GOES in an axial flux SRM (AFSRM). [ABSTRACT FROM AUTHOR]

Fractional slot concentrated winding (FSCW) permanent magnet (PM) motors are becoming an attractive solution in low-speed applications due to their superior advantages. A new topology of FSCW motor is introduced in this article, which consist of single stator and two PM rotors with different and opposite direction rated speed. The stator torque reaction is reduced significantly due to the opposite rotational direction of rotors. Some performance characteristics of proposed topology are investigated by designing and manufacturing a 0.5 kW prototype motor. The back-emf voltages, torque reaction, torque ripple and core losses are obtained via finite elements method (FEM) and are compared with two conventional FSCW motors. The prototypes of case-studied motors are tested experimentally in order to validate the advantages of proposed motor. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a 4-poles-24-slots permanent magnet (PM) homopolar machine for the flywheel energy storage system (FESS), and the operating principle is investigated. Due to the unconventional flux distribution in this machine and the goal of the design is to minimize the torque ripple while maximizing the torque density, the parameter of this machine was obtained by the 3-D finite element global optimization genetic algorithm method. In addition, the air-gap flux density of double stator, open-circuit magnetic field distribution, flux linkage, back electromotive force stator, core loss, external characteristic were analysis, and the operating principle is verified by open-circuit magnetic field distribution. It was found that core loss can be reduced almost 34% by comparing with a heteropolar PM machine, which demonstrated that the homopolar machine is a promising candidate for the FESS. A prototype has been manufactured and tested to validate the finite-element and theoretical analyses. [ABSTRACT FROM AUTHOR]

This paper proposes the analytical design methods of axial flux-switching permanent magnet (AxFSPM) machines. The analytical design methods take the influences of electric and magnetic loadings into account to calculate the specific sizing and scalability of the AxFSPM machine. In addition, the winding functions are implemented to derive the self-, mutual-, d-axis, and q-axis inductances. The results of analytical design methods indicate that the magnetic loading has bigger impact on the stator dimensions of AxFSPM machines than the electrical loading. The d- and q-axis inductances of the all-pole-wound AxFSPM machines are similar under the same number of slots and turns. A prototype is manufactured using analytical design methods. The experimental results show that the prototype machine achieves target specification and the usefulness of the proposed design method is verified. [ABSTRACT FROM AUTHOR]

Pulsed power technology is widely used in medical treatment, military, and scientific research, such as laser burst and electromagnetic launch. Compensated pulsed alternator (CPA) is a kind of device generating that pulsed power. One of the shortages for the air-core pulsed alternator is the huge excitation loss. In order to solve the problems, a multidisk axial flux CPA (MAFCPA) is proposed, which replaces the excitation windings with permanent magnets, saving the self-excitation process. In addition, multidisks are designed, especially to reduce subtransient reactance when the CPA discharges, which contributes to increasing the discharging current. This paper mainly focuses on researching the feasibility of MAFCPA in aspects of thermal issues, rotor statics, and dynamics problems. First, the topology and principle of MAFCPA are introduced, and the properties of the materials are listed as well. Second, the loss of discharging is calculated and the temperatures of both stator and rotor are solved. Then, the maximum stresses of different materials are obtained. Afterward, the critical speeds are researched in order to avoid resonance. Finally, the conclusion is made that MAFCPA can work safely under a speed of 10000 r/min and supply a pulse of over 50 ms. [ABSTRACT FROM AUTHOR]

This paper provides a thorough, parametric comparison of axial and radial flux coaxial magnetic gears with surface-mounted permanent magnets. While both topologies share similar operating principles and can achieve comparable shear stresses, they exhibit different scaling trends with respect to key design parameters. Both topologies’ volumetric torque densities (VTDs) increase with the outer radius, but the axial flux topology's VTD increases with the radius at a much faster rate than the radial flux topology's VTD. Another difference between the topologies involves their cross-sectional scaling parameters. The stack length axially scales radial flux gear cross sections, and, as it increases, the impact of end-effects decreases, which improves the performance. For axial flux gears, the radii ratio scales the cross section's radial width between different radii. This fundamentally changes optimal parameter values and design performance tradeoffs. Finally, axial flux rotors experience significant axial forces, but the radial forces on radial flux rotors can be balanced out. Based on these trends, radial flux gears are superior to axial flux gears for most applications; however, axial flux gears have a significant advantage when a large radius and a small axial length are permissible or when mechanical power needs to be transmitted across a flat barrier. [ABSTRACT FROM AUTHOR]

The effect of the back iron for a new-designed permanent magnet (PM) generator is explored in experimental and theoretical basis. The machine has been designed for wind energy turbines having a power range of 500 W. It is a three phase generator with a stator at the middle and two rotors at both sides with 32 rare-earth magnets. The study includes the 3 D finite element analysis with and without the back iron component. For two cases, electromagnetic analyses have been performed and output waveforms, power, and losses are calculated by finite element analysis and the experimental findings have been discussed. The comparison for two cases has been performed by adding different electrical resistive loads. It has been pointed out that the power from experiment and theory can change due to the air gap difference in the experiment; however, back iron plays an important role to increase the generated power and amplitude and it does not lower the losses significantly. The thermal feature of the new machine is promising, since the axial flux (AF) structure creates natural shear flow in radial direction due to the air channels inside the axis, which transfers air into the central region of the machine. [ABSTRACT FROM AUTHOR]

In this paper, a novel multidisk axial flux compensated pulsed alternator (MAFCPA), excited by permanent magnet (PM), is proposed and investigated in aspects of operational principle and pulsed performance. The design purpose of MAFCPA mainly focuses on reducing the subtransient reactance while discharging, which contributes to increasing discharging power. In detail, the compensated shield made of aluminum alloy can decouple the mutual-inductance among windings in different disks. By connecting the windings with little mutual-inductance in parallel, the purpose of reducing the subtransient reactance is achieved. Besides, to some extent, the shield helps protecting the PM as well. Both functions above are proved in analytical equations and equivalent models. Based on the equations and the models, a 0.6-MW MAFCPA in finite element analysis (FEA) is built and simulated. It appears to be a feasible scheme for pulsed alternator. [ABSTRACT FROM AUTHOR]

In this paper, a new class of reliable gearless motors, dubbed as the magnetic steering (MS) motor, is proposed to realize the concept of the magnetic differential (MagD) system for direct-drive electric vehicles. While the electronic differential (ED) system can control two individual motors to provide the differential action in the absence of mechanical differential, it suffers from reliability concerns upon errors from the individual motors. The proposed MagD system instead utilizes the MS-field excitation to interlock the magnetic fields in two rotors of the MS motor. With the control of MS-field excitation, the two rotors can be differentiated to generate appropriate torque levels for two driving wheels. As a result, the MagD system can offer higher reliability than the ED system. The machine performances of the proposed MS motor are evaluated by finite-element analysis, and the operating performances of the proposed MagD system are testified by system-level simulation. [ABSTRACT FROM AUTHOR]

In this paper, a study on an Axial Switched Reluctance Motor (ASRM) is provided and comparisons with an equivalent Radial Switched Reluctance Motor (RSRM) are established. A 3D Finite Element (FE) model is used for the ASRM and only 2D FE model for the radial one in order to reduce the computation time. First, a bibliographic review and descriptions of the two motors are given. Secondly, comparisons between both structures are proposed including flux linkages, developed torques, masses, torque-speed curves and cartography of minimum torque ripples. In order to make the comparisons more reliable, optimized control parameters and full operating range for electric vehicle (EV) power train are taken into account. [ABSTRACT FROM AUTHOR]

The thermal management of an axial flux permanent magnet (AFPM) machine is essential because it determines the machine's continuous power output and reliability. In this paper, a secondary cooling method is proposed using rotor cooling, which allows better thermal management on the permanent magnets that are attached to the rotor. This will reduce the potential of the machine failing due to magnet demagnetization and degradation. Thermal analysis via lumped parameter networks is usually sufficient in predicting the motor's thermal behavior. However, the accuracy of the prediction can be increased, especially for the devices with complex flow regions by computational fluid dynamics. In this study, the fan blade was attached to the rotor of a yokeless and segmented armature machine for flow validation and then three different fan blade designs from other engineering applications were tested. The evaluation includes the flow characteristic, power requirement, and thermal characteristic for the AFPM's rotor cooling applications. Additionally, the rotor cooling performance index is introduced to assess each fan design performance. [ABSTRACT FROM AUTHOR]

Designing an axial flux permanent magnet machine is complex and computationally intensive. This paper proposes a new closed-form method for concurrent design and analysis of a multi-stage axial flux permanent magnet machine. The method will provide a simpler modeling solution to machine designers. By calculating magnetic and electric properties, the design space of an axial flux permanent magnet is created for initial design. This paper demonstrates the feasibility of the new closed-form method by showing that the results obtained from the proposed method correlate with the finite element analysis results. The design space is also evaluated and analyzed by taking into account various parameters, including copper losses, permanent magnet density, phase voltages, and torque waveform. Finally, a multi-objective analysis is performed to compare two different designs of an axial flux permanent magnet machine. The proposed method also provides a useful guide for the initial design state. [ABSTRACT FROM AUTHOR]

Effect of bed geometry on the hydrodynamics of slot-rectangular spouted beds was studied by means of CFD-DEM simulations. Axial and lateral velocity distributions of particles as well as axial gas velocity distribution were used for validation of the simulation with experimental data. Static bed height and U 0 / U ms were constant in all simulations. Minimum spouting velocity as well as velocity, voidage and axial flux distributions of particles were determined and compared for six bed cone angles (20°–70°). An improved correlation for minimum spouting velocity was proposed which includes the effect of bed cone angle for the first time. Novel curved bed geometry, inspired from improvement of particle motion, was also proposed. Solids circulation rates for beds with different cone angles were evaluated by tracing sample particles in the bed. Axial distribution of lateral solids flux, which shows the insertion location of particles from annulus to spout, was determined for different cone angles. Combination of solids circulation rate (speed of circulation) and lateral flux (quality of circulation) was used to discuss about the effect of geometry on the circulation of particles. The best circulation behavior was observed in the curved bed. [ABSTRACT FROM AUTHOR]

In this paper, a vernier permanent magnet (VPM) machine with dual-rotor toroidal-winding axial-flux topology is analyzed. Through the combination of toroidal windings with the rotor-stator-rotor topology, the end winding length of the proposed machine is significantly reduced compared with that of the regular VPM machine. Based on the airgap permeance function, the back-EMF and torque expressions are derived and the nature of the machine is revealed. The influence of pole ratio (ratio of rotor pole pair number to stator pole pair number) and main geometric parameters, such as slot opening, magnet thickness, etc., on electromagnetic performance is then analytically investigated in detail. Both the quasi-three-dimensional (quasi-3D) finite element analysis (FEA) and 3-D FEA are applied to verify the derived equations. Finally, a prototype of the proposed machine has been manufactured and experimentally evaluated. The test results agree well with both theoretical and FEA analyses. With the current density of 5.8 A/mm 2 and slot fill factor of 0.35, the torque density of the proposed machine prototype can reach 31.9 kNm/m 3. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) method is the most widely used non-destructive testing techniques for detection and characterization of defects in product transmission pipelines. The maximum safe operating pressure is a crucial parameter in practice, which is predicted with respect to the length, width, and depth of defects. In a previous work, an algorithm is devised to detect and estimate the width of the defect based on MFL signals. In this paper, an efficient method based on axial MFL level contours is devised to estimate the length of the defect. This method uses the patterns of signal level contours in the region corresponding to the defect’s area. In addition, a Gaussian radial basis function neural network (NN) is trained to approximate the depth of the defect. The NN is fed with the estimated length, width, and signal peak-to-peak values, and the output of the network is the estimated depth. The proposed detection and estimation method is applied to MFL measurements to detect and determine the sizing of metal loss defects. The efficacy and accuracy of the proposed methods are examined through a rich set of sample defects that contains simulated defects, designed defects that are carved on a real pipe by milling, and actual pigging data validated by several dig up verifications. Obtained results confirm the effectiveness and accuracy of the proposed depth and length estimation method along with the previously devised detection and width estimation methods, in characterization of metal loss defects. [ABSTRACT FROM AUTHOR]

The axial magnetic-field-modulated brushless double-rotor machine (MFM-BDRM) is a novel possible alternative power-split device for hybrid electric vehicles (HEVs). This paper proposes a two-dimensional (2-D) analytical method to predict the performance of the axial MFM-BDRM to reduce computing time. The computation is based on the solution of Laplace's or Poisson's equation with boundary conditions for each elementary rectangular region. By taking account of the existence of modulating ring and the stator slotting effect, the proposed model is able to calculate magnetic-field distribution with high accuracy. In order to assess the proposed method, the 2-D analytical and three-dimensional (3-D) finite element analysis (FEA) results have been compared, and good agreements have been achieved. As the analytical computation is much faster and more flexible, the proposed method can be used in the preliminary design process of the axial MFM-BDRM. [ABSTRACT FROM AUTHOR]

A computationally efficient method is presented to investigate additional cogging torque harmonics resulting from misalignment of the rotor and stator caused by assembly and manufacturing tolerances in an axial flux fractional pitch permanent magnet synchronous machine (PMSM). The superposition method creates a complete cogging torque profile by using a library of pole transitions over a single stator slot. The method extends previously published work, and is used to predict the effect of eccentricity misalignment in combination with pole and slot placement inaccuracies on cogging torque. Experimental data are presented supporting the superposition data indicating that static and dynamic eccentricity produce first- and second-order sidebands about the rotor and stator affected harmonics, respectively. There is good agreement between the hybrid superposition method, FEA, and measured experimental data. [ABSTRACT FROM PUBLISHER]

This paper introduces the design and analysis of a new hybrid hysteresis motor with combined axial and radial flux rotors aiming to improve the poor performance characteristics of the conventional hysteresis motors such as the output torque and efficiency. The proposed hybrid design incorporates the advantageous features of both the conventional axial and radial flux hysteresis motors (RFHMs) in a unique structure. The design aspects and constraints of the proposed machine are based on a prestudied single-sided axial flux hysteresis motor (AFHM). In order to analyze the electromagnetic performance of the proposed structure and investigate the geometry specifications of the designed machine, a three-dimensional (3-D) finite-element analysis (FEA) is conducted. The hysteresis loop modeling is done based on the elliptical approximation of the hysteresis loop by considering the saturation during the FEA with an iterative method. Finally, in order to investigate the electromagnetic performance of the proposed device and the accuracy of the design and analysis approach, a prototype is built. The test results validate the good performance of the proposed machine. [ABSTRACT FROM PUBLISHER]

This research attempts to find a new closed-form solution for axial flux permanent-magnet (AFPM) machines and applies it in a traction application example. The machine types considered are with toroid and overlapping windings. The proposed closed-form solution includes analytical derivations for winding lengths, resistances, and inductances as functions of fundamental air-gap flux density and inner-to-outer diameter ratio. Finite-element analysis is used to verify the accuracy of the proposed analytical calculations. Furthermore, a parametric analysis is performed on inductances, resistances, phase back-EMFs, phase terminal voltages, efficiencies, and torque speed capability to compare for both winding types. The proposed solution should assist traction machine designers to ascertain benefits and limitations of the toroid and overlapping winding types in traction application as well as to achieve faster design results. [ABSTRACT FROM AUTHOR]

Axial structures of the hysteresis motors, similar to the other axial types of electrical machines, have some outstanding characteristics with regard to radial structures, such as higher torque-to-weight ratio, excellent efficiency, adjustable airgap, and balanced rotor–stator attractive forces. Since the accurate measurement of the hysteresis machine characteristics by prototyping and testing is expensive and time consuming, in this paper, the finite-element analysis is adopted for the prediction and analysis of an axial flux hysteresis motor. The analysis is conducted based on the elliptical approximation of the hysteresis loop. Since the elliptical approximation is not able to model the saturation of the hysteresis loop, an iteration-based method is proposed to overcome this problem and increase the analysis accuracy. Finally, in order to investigate the proposed model accuracy, the device is prototyped, whose experimental results agree well with those extracted from the analytical model. [ABSTRACT FROM AUTHOR]